What would make people cooperate with strangers?

The study aimed to find out which between group norms (cohesion ) and reciprocity is a more powerful inducement of cooperation among humans was published in Psychological Science.

To get their answers, the researchers recruited hundreds of participants online for a two-part experiment. A group of six would engage in a “survival task”—prioritizing a list of items needed for survival on a spaceship travelling to the moon—to help them form a cohesive group. Then, individual group members were paired up with a new participant—a “partner”—to play the Prisoner’s Dilemma game.

In the game, participants were given 100 chips and told they could give all, some, or none to their partner, with that number doubling for the recipient. So, if they gave 50 chips, their partner received 100 chips. They were also told their partner would be given the same opportunity to give back to them. The number of chips served as a proxy for their willingness to cooperate.

Before deciding what to give, participants were shown how their partner had allegedly behaved in the Prisoner’s Dilemma game with other members of the six-person group. Unbeknownst to the participant, this was false information that presented one of four possible scenarios: 1) fellow group members gave away almost all of their chips and so did the partner; 2) group members gave almost nothing away, as did the partner; 3) group members gave away almost all of their chips, but the partner gave almost nothing; 4) group members gave almost nothing, while the partner gave away almost all of the chips.

After analyzing the results, the researchers found that participants cooperated under scenario 1 and didn’t under scenario 2. No surprises there. But, in the more ambiguous situations, participants continued to cooperate with a cooperative partner, even if their group was not cooperative. And they didn’t cooperate as much with an uncooperative partner, even if fellow group members did. This suggests that reciprocity is a stronger factor in cooperation than group conformity.

“We were surprised by these findings—especially the size of the effect—because past research found that individuals tend to conform with their groups even when the group is clearly wrong,” says the lead author of the study, Angelo Romano. “Reciprocity was able to outperform conformity to promote cooperation.”

These results held even when the six-person group’s most influential member was observed not giving chips to a very cooperative partner.

A version of this article appeared on the greater good science website.

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